Field Of The Invention
The present invention relates to a new and useful container case and more particularly to a container case made from a blow molding process. Even more specifically, the present invention relates to a blow molded container case having a new and improved hinge, also made from a blow molding process, for joining the main body parts of the container case together.
It is well known in the art and advantageous to form separately the main body parts of a container case, usually a base and a cover, and to then assemble these parts together to form the finished product. So that the parts cooperate to allow the case to be opened and closed, a hinge is provided which is preferably simple in construction to allow the manufacturer to quickly and easily assemble the case. In designing container cases, the hinge is usually one of the weakest points on the case and often enough fails prematurely. Therefore, although it is desirable to make the hinge as simple as possible, it should also be strong enough to withstand wear and tear caused by normal use of the case and also abnormal use, for instance, when the container case is forced open wider than it is designed to open. For the purpose of increasing the strength of the hinge, many manufacturers prefer to form the hinge integrally with the body parts of the case.
Since the advent of blow molding, it has become popular in the industry to form container or carrying cases from a thermoplastic material using the process. Advantageously, the hinge can be formed integrally with the body parts of the case from the same parison material forming the body parts. In many instances where the body parts of the case consist of a cover and a base, the cover and base include separate portions which cooperatingly mate to form the hinge when the case is assembled. Whether or not the case parts are injection molded or blow molded or single-walled or double-walled in construction, it is the usual practice to form solid plastic hinge portions by compression molding. During assembly of the case, the hinge portions integrally joined to the cover and base are aligned end-to-end along a common axis, drilled in the axial direction entirely through their combined length and pinned usually with a steel rod to form a typical container case hinge.
There are many inherent disadvantages of the conventional container cases having compression molded hinge portions integrally formed with the case parts. One such disadvantage exhibits itself during assembly. Because the mating hinge portions must be drilled to form a receiving bore for a pin, quite often the drill wanders off center from the common axis during the drilling operation and breaks through the sidewall or corner edge of one of the hinge portions. In that situation the case must be scrapped.
A second disadvantage of the conventional case described above is that it typically uses a steel pin to join the hinge portions together. The steel pin is usually loosely seated in the receiving bore and, if the ends of the pin are not hooked or flared, may work itself free of the bore. This may be caused by either the bore being formed with a diameter greater than that of the steel pin or, through normal flexing of the hinge, the bore's diameter increasing from wear due to the steel pin.
If upon final inspection before shipment, a defect in the case is noticed, the manufacturer will sometimes try to save costs by melting the defective case into a thermoplastic material and reusing the material to form another case. If steel hinge pins are used, they must of course be removed before the case is melted. Additional time is thus required to disassemble the defective case before melting it down into a thermoplastic material for reuse.
The cover and base of the typical container case are usually further provided with a stop or rest in the form of an extension situated near the hinge. The purpose of this stop or rest is to prevent the case from opening too far, that is, to allow the cover to move pivotally relative to the base no more than a predetermined arc. In many instances, the stop may comprise a pair of raised portions of the cover and base which are aligned to contact each other when the case is fully opened. Although the stop is adequate in many applications, there are instances when excessive force applied to open the case is transmitted to the hinge by the leverage of the stop to cause the hinge to rupture.